The biggest excuse people make for traveling in sloppy sweats, oversized-tees, and shorts is that they are more comfortable. But looking stylish doesn't mean you have to be uncomfortable! A stripe knit top is just as comfortable as a t-shirt, and I think skirts are even more comfortable than shorts or jeans.
PS - Longchamp bags are great for travel and right now they are 20% off at Nordstrom! These bags rarely go on sale, so if you have been wanting one, now is the time to buy!